Two whales slaughtered off coastal Japan were found with elevated levels of radioactive cesium.

Two minke whales caught by Japanese whalers off the country’s northern coast contained radioactive cesium that is believed to be from the crippled Fukushima nuclear power plant.

The two marine mammals were among 17 caught and slaughtered off Hokkaido Island under the country’s so-called research whaling program.

The contamination in one whale was measured at 31 becquerels per kilogram, well below the temporary upper limit of 500 becquerels per kilogram set by the government. The other whale had a slightly lower amount of the isotope.

“The levels are far below the limit, and the meat from the catch is safe for consumption,” Fisheries Agency official Kosei Takekoshi told reporters.

The government has banned fishing around the Fukushima plant, and officials conduct weekly radiation monitoring of seafood in coastal waters.